The present disclosure relates to semiconductor packages. It finds particular application in conjunction with frame lids for enclosing electronic components in a semiconductor package, and will be described with particular reference thereto. More specifically, methods for making such frame lids with reduced defects are described herein, as are the frame lids formed thereby and electronic packages including such frame lids. However, it is to be appreciated that the present disclosure is also amenable to other like applications.
Frame lids are used for hermetically sealing certain electronic components in semiconductor packages. Hermetically sealed electronic packages can be made by placing a frame lid over an electronic component mounted within a cavity of an insulating package base. Traditionally, a metal substrate is stamped to provide a surface on the formed lid for soldering the lid to a package base which has been mounted to the electronic components. After stamping, the surface is nickel plated, followed by plating of the surface with a thin layer of gold. A solder (e.g. a lead-free or lead-based alloy) preform whose shape corresponds to the area to be soldered is placed on the gold layer. To hermetically seal the package, the solder is heated to cause it to flow. Soft solder has a relatively low melting temperature, so sealing can be performed at a low temperature.
When the frame lid is made of a non-metallic material, the frame lid must be metallized to form a metal layer on the periphery of the surface to enable the frame lid to be bonded by soldering. This adds to the production costs of the frame lid.
Some issues can arise with the metallized layer on the frame lid. First, the mask used to metallize the peripheral area can be offset (i.e. incorrectly registered), resulting in different widths of the metallized portion around the periphery of the frame lid and potentially weakening the hermetic seal on the portion that is now thinner than intended. Second, the metallized layer can pull back from the edges of the lid, creating gaps and again potentially weakening the hermetic seal. Outgassing can also occur due to organic content in the metallized layer. These can result in leak failures, delamination, poor bonding, etc. In addition, issues can arise with the solder, such as solder voids, dewetting, splatters, and PIND failures (when excess solder forms particles inside the cavity).
It would be desirable to develop an alternate method for producing frame lid assemblies that minimize these defects.